a) Field of the Invention
The invention is directed to an arrangement for laser coagulation at the ocular fundus with at least one illumination light source for an illumination beam path, with a laser arrangement for generating a sighting beam path and a treatment or therapy beam path, wherein the sighting radiation and therapy radiation have different wavelengths, with observation optics for visual observation of the ocular fundus, for selecting the coagulation site and/or for monitoring the results of coagulation, and with a protective mechanism which prevents the laser radiation from penetrating into the eye of the person administering treatment. An individual laser with a plurality of different laser light wavelengths and the combination of a plurality of lasers with different wavelengths and corresponding driving circuits are also possible as a laser arrangement for radiating the sighting radiation and therapy radiation.
b) Description of the Related Art
In laser coagulation on the human eye, the desired therapeutic effect is achieved by thermal alteration of tissue in selected areas of the ocular fundus. For this purpose, energy in the form of laser light pulses is introduced into the tissue. With pulse lengths of 20 to 1000 milliseconds and outputs of around 200 mW, the radiated energy is absorbed, so that the surrounding tissue is heated locally. The success of the coagulation can be identified by a whitish color (necrosis) at the coagulation site and can be observed and monitored by the treating person through visual inspection of the ocular fundus, e.g., by means of a slit lamp. The end of the treatment is determined by observation based on subjective appraisal.
Since the observation light as well as the sighting radiation and therapy radiation penetrate into the patient's eye and are reflected therein during a treatment of this kind, the eye of the treating person is also always at risk and it is accordingly necessary to protect the eye of the treating person from reflected therapy radiation.
According to known prior art, in order to prevent injuries resulting from the reflected therapy radiation, separate component groups or subassemblies are used for the reflection of the therapy radiation into the observation beam path and the optical coupling out of the therapy radiation from the radiation reflected by the ocular fundus before this radiation reaches the eye of the treating physician. In particular, the use of eye protection filters which are swiveled into and out of the radiation coming from the ocular fundus by means of mechanical devices is known.
Since known devices comprise a plurality of component groups and/or must be composed of a number of structural component parts, they have the disadvantage that assembly of such arrangements is complicated and requires extensive space, which undermines the effort toward more economical and also miniaturized medical instruments. In addition, an increasing number of parts in the protective devices require swiveling mechanisms which are more complicated and therefore more susceptible to malfunction. In the event of failure of the swiveling mechanisms, the eye protection filter cannot be swiveled into the beam path and the dangerous therapy radiation can reach the eye of the treating physician.